EP0081650B1 - Apparatus for reading an angularly multiplexed optical recording medium - Google Patents

Apparatus for reading an angularly multiplexed optical recording medium Download PDF

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Publication number
EP0081650B1
EP0081650B1 EP82109402A EP82109402A EP0081650B1 EP 0081650 B1 EP0081650 B1 EP 0081650B1 EP 82109402 A EP82109402 A EP 82109402A EP 82109402 A EP82109402 A EP 82109402A EP 0081650 B1 EP0081650 B1 EP 0081650B1
Authority
EP
European Patent Office
Prior art keywords
light
photodetectors
tracks
pair
track
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82109402A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0081650A3 (en
EP0081650A2 (en
Inventor
William V. Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Discovision Associates
Original Assignee
Discovision Associates
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Discovision Associates filed Critical Discovision Associates
Priority to AT82109402T priority Critical patent/ATE18615T1/de
Publication of EP0081650A2 publication Critical patent/EP0081650A2/en
Publication of EP0081650A3 publication Critical patent/EP0081650A3/en
Application granted granted Critical
Publication of EP0081650B1 publication Critical patent/EP0081650B1/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
    • G11B7/24073—Tracks
    • G11B7/24076—Cross sectional shape in the radial direction of a disc, e.g. asymmetrical cross sectional shape
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2407—Tracks or pits; Shape, structure or physical properties thereof
    • G11B7/24085—Pits
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/005—Reproducing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor

Definitions

  • the present invention relates to the field of information recording media, and more particularly to an apparatus for reading an optically readable recording medium as referred to in the preamble of claim 1.
  • An optically readable storage medium is one which can be read by way of a beam of light which is imaged to a small spot on the medium.
  • Information is stored on a disc in uniform circular or spiraling tracks of optically readable indicia. By arranging indicia in row-like tracks, a spot of light can be scanned along a track and the variation in the intensity of the light reflected directly back may be detected to extract the information from the disc.
  • the amount of information that can be stored on an optical disc depends upon the packing density of the indicia. Consequently, tracks and the indicia within them are spaced as close together as possible.
  • This track spacing permits the optical disc to be played while the imaged spot of the light scans along the track, wobbling back and forth within the limits of the range of the servo control mechanism of the disc player, while maintaining the influence of adjacent tracks, called "cross-talk", to an acceptable minimum for video program playback. Closer track-to-track spacing in this format has been found to result in a rapidly increasing level of cross-talk to unacceptable levels.
  • EP ⁇ A1 ⁇ 26517 teaches to position adjacent information tracks at different slopes, so that during the read-out of a first track the radiation coming from a second adjacent track cannot reach a radiation-sensitive detector employed for read-out.
  • the track distance may be half that of known record discs. While increasing the information density cross-talk is kept on a lower level. By shifting or dividing the reading light beam both the tracks can be read simultaneously by a detector for each one.
  • any light which "spills over" to adjacent tracks from the reading spot of light results in the production of associated cones of light inclined at a different angle from the cone of light emanating from the track being read.
  • This provides an effective attenuation of the influence of the information recorded on adjacent tracks on the active photodetector, and thereby reduces the level of cross-talk between adjacent tracks in optically readable recording media.
  • Figure 1A is a plan view of a conventional optical disc used for the recording and playback of video program information.
  • Figure 1B is an edge view of the disc shown in Figure 1A.
  • the disc is circular and flat, approximately the size of an LP phonograph record.
  • the disc has a central aperture 12 through which the spindle of an optical disc player is inserted for the support and rotation of the disc 10.
  • Information is recorded on the disc 10 in an annular area of recording surface 14 having an inner radius somewhat larger than the central aperture 12, and having an outer radius somewhat smaller than the outer radius of the disc 10.
  • the disc is formed from two separate disc parts 16,18, as can best be seen in Figure 1B, which are glued together to ' form a single, two-sided disc.
  • the recording surface 14 can be read by a conventional optical disc player apparatus.
  • Figure 2 is a plan view of a tiny section of the recording surface 14 of one part 16 of the optical disc 10 shown in Figures 1A and 1B. Three adjacent tracks 22, 24 and 26 of indicia 28 are shown. The indicia 28 are arranged in rows in each track. The length and spatial frequency of the indicia 28 are varied in accordance with the information recorded on the track.
  • Figure 3 is a cross-section through line 3-3 of Figure 2, illustrating the structure of the indicia 28 which make up the information tracks of the optical disc 10.
  • Figure 4 is a cross-section through line 4-4 of Figure 2 illustrating a cross-section of the indicia 28 in the direction of their width.
  • the indicia 28 comprise long narrow pits in the information surface 14 of the disc side 15. Since the reading spot of light is formed by a beam of light which passes through the disc part 16 from the side 30 opposite the information surface 14, the indicia 28 are presented as a series of bumps to the incident light.
  • the nominal value for the spacing between indicia along the tracks for commercial video optical discs is approximately 1 micron.
  • Track-to-track spacing, or "pitch" for such discs is approximately 1.6 microns. This track spacing of 1.6 microns represents what has been considered in the industry to be the minimum practical track pitch which provides a level of cross-talk considered acceptable.
  • Optical discs having tracks of indicia of the aforementioned nominal dimensions can have recorded thereon video program information of up to 1 hour per side for discs which are played at a constant linear velocity, and up to 1/2 hour per side for discs played at a constant angular velocity.
  • Further optical discs constructed according to the prior art appear, in their large features, very similar to the optical disc 10 shown in Figures 1A and 1B, discussed above. In fact, such discs have all of the features described in connection with those figures. However, at a microscopic level the recording surfaces of such discs are quite different.
  • Figure 5 is a plan view similar to that shown in Figure 2, of a microscopic portion of the information surface 14' of a disc usable with the present invention.
  • the recording surface 14' is provided with tracks of indicia 28', e.g., 22', 24', 26' which appear similar to the tracks 22, 24, 26, of a conventional optical disc.
  • the tracks of indicia are separated by borders, e.g., 32, 34, 36.
  • Figure 6 is a section view through lines 6-6 of Figure 5 illustrating the configuration of the surface 14' which gives rise to the aforementioned borders 32-36.
  • the tracks 22'-26' are arranged so that alternate tracks are formed in inclined surfaces oriented at the same magnitude angle with respect to a planar imaginary reference surface 37 parallel with surface 30', but in opposite directions.
  • One set of surfaces 39 is oriented at an angle 6, while the other set of surfaces 41 is oriented at an angle -6 to the reference plane 37.
  • Figure 7 is a partial section view through line 7-7 of Figure 6. As may be appreciated by an inspection of Figures 6 and 7, the dimensions of the indicia 28' are substantially the same as compared with the conventional disc 10 of Figures 1 to 4.
  • Figure 8 is an orthogonal view of a section of information surface 14' showing two sets of adjacent track inclined surfaces 39, 41.
  • the curvature of the tracks has been exaggerated greatly for purposes of illustration.- It will be readily appreciated from the figure that the inclined surfaces 39,41, upon which the tracks are formed are provided in similarly inclined sets which alternate with one another.
  • the inclined surfaces 39, 41 are formed on the information surface 14' of the disc such that two separate spiraling tracks may be recorded.
  • Figure 9 illustrates this.
  • the separate path for each set of tracks, corresponding to the differently inclined surfaces, is depicted by a separate spiral.
  • the path followed by the first set of inclined surfaces 39 ( Figure 8) follows the solid line spiral track 34
  • the second set of inclined surfaces 41 follows the dashed line spiral track 36.
  • Information is stored on the disc such that first one spiral track 34 is read entirely, and then the other spiral track 36 is read, for example in the reverse direction from the first track 34.
  • Other schemes are possible, for example alternately switching slopes of a single continuous track with each complete revolution around the track on the disc.
  • the configuration shown in Figure 9 depicting alternating interleaved separate tracks is preferred.
  • FIGs 10A and 10B are optical diagrams which illustrate principles by which the optical disc can be read.
  • An objective lens 38 images a light beam 40, for example a laser light, to a small spot 42 on a track in one of the sets of sloping surfaces 39 or 41 ( Figure 8).
  • Figure 1 OA the spot 42 is shown impinging on a track in surface 41.
  • the surface has been exaggerated in lateral extent for purposes of illustration.
  • the imaged spot 42 of light impinges on the track of the surface 41 and is reflected and scattered back in a cone of light 44 having a central axis 45 oriented at an angle 26 with respect to the central axis 46 of the incident beam of light 40.
  • Cone 44 of light emanating from the track extends through an angle 8 which varies as a function of the track-to-track spacing.
  • the disc can be designed such that the cone 44 of light is predominantly on one side of a plane which includes the central axis 46 of the incident beam of light and which extends in the direction of the track.
  • the presently preferred embodiment has a track-to-track spacing of 1.2 microns, and an angular incline 8 of 15°.
  • Figure 10B is a diagram similar to that shown in Figure 10A, showing the spot 42 of light incident on track 39, which is inclined in the opposite direction to track 41, as discussed above.
  • the same considerations apply as discussed in connection with Figure 10A, only the direction of the incline of the central axis 47 of cone 48 is opposite to that of cone 44, as can be seen.
  • cones of light 44 and 48 ( Figure 10A and 10B, respectively) partially overlap the objective lens 38. Accordingly, in order to detect most of the light within each cone 44, 48, one pair of photodetectors should be located within the field of the objective lens 38 and another outside of the field.
  • Figure 11 depicts such an arrangement of photodetectors.
  • a first pair of photodetectors 50 and 52 is provided, such that photodetector 50 is outside of the field of the objective lens 38 while photodetector 52 is in the field, as shown.
  • On the opposite side of a plane 49 bisecting the objective lens 38 in the direction of the tracks is another pair of photodetectors 54 and 56, with photodetector 54 being outside of the field and photodetector 56 being within the field of the objective lens 38.
  • the outputs of an associated pair of photodetectors for example photodetectors 50 and 52, are added together, amplified and demodulated.
  • Figure 12 is a diagram of an optical arrangement by which the scheme depicted in Figure 11 may be implemented by modification of a conventional optical disc player apparatus.
  • the outer photodetectors 50, 54 ( Figure 11) are attached to the objective lens support 60, a polarizing beam splitter 62 is provided in the optical path of the incident beam 40, and a quarter wavelength plate 64 is placed in the optical path between the beam splitter 62 and the objective lens.
  • the quarter wavelength plate 64 has the effect of rotating the polarization of the incident light beam by 90 degrees after it passes through twice, once in the incident path and once after being reflected from the disc. The returning light is thus reflected at the beam splitter 62 at right angles, as shown.
  • the two inner photodetectors 52 and 56 are placed in the path of the deflected light, as shown.
  • a further advantage of splitting between two photodetectors the detection of the light returning from the angularly multiplexed disc of the present invention is that advantage may be taken of cancellation effects which serve to improve the cross-talk suppression even more.
  • the unwanted contribution of light incident on the photodetectors from adjacent tracks is additive with the desired light across a portion of its angular extent within the area being detected, and is subtractive within the remainder of its extent.
  • the unwanted component may result in an additive effect with the light detected on photodetector 52 while at the same time resulting in a subtractive effect with the light being detected on photodetector 50.
  • Figure 13 shows a circuit diagram for a circuit which implements this scheme.
  • the output of photodetector 50 is applied to the input of an amplifier 70, the output of which is applied to one input of a summer 72.
  • the output of photodetector 52 is applied to the input of a second, variable amplifier 74, the output of which is applied to the second input of summer 72.
  • the output of the summer is amplified and detected to recover the information on the track being read. By adjusting the relative amplification of amplifier 74 with respect to amplifier 70 the additive component and the subtractive component of cross-talk can be balanced until they are effectively nulled.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Optical Record Carriers And Manufacture Thereof (AREA)
  • Holo Graphy (AREA)
EP82109402A 1981-12-10 1982-10-11 Apparatus for reading an angularly multiplexed optical recording medium Expired EP0081650B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82109402T ATE18615T1 (de) 1981-12-10 1982-10-11 Lesegeraet fuer ein medium zur winkelmultiplexen optischen aufzeichnung.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US06/329,374 US4534021A (en) 1981-12-10 1981-12-10 Angularly multiplexed optical recording medium
US329374 1981-12-10

Publications (3)

Publication Number Publication Date
EP0081650A2 EP0081650A2 (en) 1983-06-22
EP0081650A3 EP0081650A3 (en) 1983-08-24
EP0081650B1 true EP0081650B1 (en) 1986-03-12

Family

ID=23285089

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82109402A Expired EP0081650B1 (en) 1981-12-10 1982-10-11 Apparatus for reading an angularly multiplexed optical recording medium

Country Status (6)

Country Link
US (1) US4534021A (ko)
EP (1) EP0081650B1 (ko)
JP (1) JPS58102339A (ko)
KR (1) KR870002143B1 (ko)
AT (1) ATE18615T1 (ko)
DE (1) DE3269858D1 (ko)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5936338A (ja) * 1982-08-24 1984-02-28 Matsushita Electric Ind Co Ltd 光デイスク記録再生方法
JPS60234232A (ja) * 1984-05-07 1985-11-20 Matsushita Electric Ind Co Ltd 光デイスクおよびそのトラツキング方法
US4870631A (en) * 1986-05-30 1989-09-26 Finial Technology, Inc. Optical turntable system with reflected spot position detection
JPH0482018A (ja) * 1990-07-24 1992-03-16 Matsushita Electric Ind Co Ltd 光ディスク再生方法および光検出器
US5268886A (en) * 1990-07-24 1993-12-07 Matsushita Electric Industrial Co., Ltd. Method and apparatus for reproducing signals using an optical disk having V-shaped grooves
JPH0492214A (ja) * 1990-08-03 1992-03-25 Matsushita Electric Ind Co Ltd 光ディスク再生方法
JPH04182935A (ja) * 1990-11-19 1992-06-30 Matsushita Electric Ind Co Ltd 光ディスク再生方法
JP3193105B2 (ja) * 1992-02-29 2001-07-30 日本ビクター株式会社 チルトエラー検出装置
JPH07230625A (ja) * 1994-02-17 1995-08-29 Pioneer Electron Corp 光記録媒体並びにその記録装置及び再生装置
JP3723179B2 (ja) 2003-01-16 2005-12-07 幸一郎 内藤 自走船台

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US3235672A (en) * 1961-11-17 1966-02-15 American Optical Corp Optical sound recording and reproduction
US3513268A (en) * 1966-08-30 1970-05-19 Bell & Howell Co Optical recording and reproducing systems including noise reducing means
US3530258A (en) * 1968-06-28 1970-09-22 Mca Technology Inc Video signal transducer having servo controlled flexible fiber optic track centering
FR2069448A5 (ko) * 1969-11-15 1971-09-03 Licentia Gmbh
FR2266932B1 (ko) * 1973-03-02 1977-09-02 Thomson Brandt
JPS5442266B2 (ko) * 1973-07-27 1979-12-13
US3919465A (en) * 1974-01-14 1975-11-11 Zenith Radio Corp Optical system for directly detecting spatially recorded signals
US3992593A (en) * 1974-08-22 1976-11-16 Heine William K Disc phonograph record playback by laser generated diffraction pattern
JPS5953612B2 (ja) * 1975-11-19 1984-12-26 カブシキガイシヤ フジテレビジヨン コウデンシキサイセイホウホウ
JPS5264215A (en) * 1975-11-21 1977-05-27 Pioneer Electronic Corp Optical signal reader
JPS5920170B2 (ja) * 1976-02-05 1984-05-11 三菱電機株式会社 情報再生装置
GB1603596A (en) * 1977-06-06 1981-11-25 Mca Disco Vision Optical transducer and focusing system
US4142098A (en) * 1977-07-05 1979-02-27 Zenith Radio Corporation Optical readout for reflective video discs
US4193090A (en) * 1977-08-15 1980-03-11 Zenith Radio Corporation Optical detection system for simultaneously interrogating a plurality of tracks
NL7805069A (nl) * 1978-05-11 1979-11-13 Philips Nv Inrichting voor puntsgewijze aftasting van een infor- matievlak.
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JPS5680838A (en) * 1979-11-30 1981-07-02 Seiko Instr & Electronics Ltd Optical information reader
US4349901A (en) * 1980-06-20 1982-09-14 Eastman Kodak Company Apparatus and method for reading optical discs
JPS57105828A (en) * 1980-12-19 1982-07-01 Matsushita Electric Ind Co Ltd Optical disk recording and reproducing system

Also Published As

Publication number Publication date
KR840003108A (ko) 1984-08-13
US4534021A (en) 1985-08-06
DE3269858D1 (en) 1986-04-17
JPH0338657B2 (ko) 1991-06-11
ATE18615T1 (de) 1986-03-15
KR870002143B1 (ko) 1987-12-12
EP0081650A3 (en) 1983-08-24
EP0081650A2 (en) 1983-06-22
JPS58102339A (ja) 1983-06-17

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